1. Field of the Invention
This invention relates generally to semiconductor transducer devices. In particular, this invention relates to forming a wide semiconductor transducer device by arranging a plurality of semiconductor transducer device subelements in a linear array.
2. Description of Related Art
Wide semiconductor transducer devices are well known. Examples of such wide semiconductor transducer devices include page-width-wide electro-optical semiconductor sensors, such as photodiode arrays (CCDs) or the like, which are used in facsimile machines, image scanners and xerography machines. Another example of a wide semiconductor transducer device is a page-width-wide electro-optical semiconductor printbar, such as printbars formed of arrays of semiconductor light-emitting diodes (LEDs) or the like. A third example of a semiconductor transducer device is the array of semiconductor heater elements used in page-width-wide direct thermal printbars or page-width-wide thermal ink jet printbars. A common feature of all of these wide semiconductor transducer devices is the demand by users of such devices for input or output resolutions of 300 pixels per inch to 600 pixels per inch or better.
One known method for forming such wide semiconductor transducer devices is to form the full semiconductor transducer device out of a linear array of semiconductor transducer device subunits. A plurality of semiconductor transducer elements is formed in a linear array or along multiple lines of each of the semiconductor transducer device subunits at a spacing corresponding to the desired resolution. The associated transducer circuits for each of the plurality of transducer elements formed on a transducer subunit are also formed on the semiconductor transducer subunit. The associated transducer circuits are often switches to activate heater elements or pass transistors and amplifiers for photo site signal or information access. Frequently, the associated circuit elements take up a large surface area compared to the transducer elements themselves.
Each subunit requires that the first and last transducer must be located close to the lateral edges of the subunit. The subunits must also be butted together or positioned in close proximity, so that the relative spacing between the edge transducers on adjacent chips is the same as the spacing between transducer elements within a chip.
As the resolution of wide semiconductor transducer devices has risen, the center-to-center spacing between adjacent transducer elements has fallen. For instance, in the case of a 600 pixel per inch thermal ink jet printer using a wide semiconductor transducer device, the center-to-center spacing is on the order of 42-43 microns. As the transducer element itself is on the order of 25-26 microns wide, the distance between the right edge of the left hand one of a pair of adjacent transducer elements and the left edge of the right hand transducer element is on the order of 12 to 14 microns. Accordingly, to ensure constant spacing along the entire semiconductor transducer device, the leftmost and rightmost transducer elements on one of the semiconductor transducer device subunits must be placed within 6 to 7 microns of the side edges of the semiconductor transducer device subunit.
However, when the semiconductor transducer device subunits are diced or cut from a semiconductor wafer during processing, cutting the chip out of the wafer can cause structural damage to the transducer device subunit or chip. A damage zone extends into the chip, in a direction perpendicular to the line of cut, up to 10 to 20 microns away from the edge. While the transducer elements themselves are usually sufficiently structurally robust to withstand the damage caused by dicing, the associated transducer circuits are usually not robust enough to withstand the dicing damage. Accordingly, while the small size of the transducer elements makes the probability of damage to them small, the associated transducer circuits within the zone of dicing damage are usually damaged during dicing. Such damage usually renders the corresponding transducer element inoperative, requiring costly post-processing repairs at best and making the semiconductor transducer subunit worthless for its intended purpose at worst.
Further, while the transducer elements are usually sufficiently robust, they are still susceptible to dicing damage. Thus, the yield of the process for making the transducer chips is not 100%, as some chips are still lost through dicing damage. However, the yield is optimized by locating the associated transducer circuitry (and the transducer elements) away from the chip edges.